A conventional cooking heater using a high frequency is a microwave oven depicted in FIG. 10. A cooking heater 1 had a front door 2 through which a user can insert or remove foods to/from a chamber 3. A high-frequency-generator 4 is disposed in the cooking heater 1, and the high frequency is irradiated into the chamber 3 through an irradiation opening 5 formed on a ceiling of the chamber 3. The irradiation opening 5 is not always formed on the ceiling, but it may be formed on a rear face or side face. The irradiation opening 5 may be formed in plural. A humidity sensor 6 senses humidity produced by the cooking. The user can identify the cooking progress by using the humidity sensor 6. A weight sensor 7 adjusts a cooking time depending on a weight of each food. These sensors are not always used together, but are used independently or used with other sensors.
When cooking foods by such a cooking heater using a high frequency as described above, several cooking methods are available: (1) heating for a predetermined time, (2) automatic cooking through controlling the operation according to a humidity and weight detected by the sensors, (3) programmed cooking which specifies an output of high frequency and irradiation time in detail. Since these methods are used properly for types of foods, quantities and details of cooking, a good result is obtained depending on a condition.
However, heat values from each food by high-frequency-heating are not the same but differ from each other, therefore, in principal, fine temperature adjustment is difficult for this heating method. It is also difficult for this high-frequency-heating to heat foods uniformly. In the case of heating a plurality of foods simultaneously in the chamber, not only types of foods and quantities, but also location of foods within the chamber changes the heating characteristics. Uniform heating of plural foods thus becomes much more difficult. The problem of uniform heating when heating up plural foods simultaneously is also found in cooking heaters other than the high-frequency cooking heater. For example, when using an oven having a heater on its ceiling, the nearer a food is placed from the ceiling, the sooner the food is heated, and the farther is a food placed to the heater, the slower the heating process. In the case of a convection oven, uniform heating over all of the foods is also difficult, and uneven heating inevitably occurs due to a location of the hot air outlet and placement of food in the chamber.
Although the conventional cooking heater has a function for heating the foods uniformly without unevenness as stated above, it has still a drawback that it cannot heat up plural foods uniformly and simultaneously.
The invention overcomes the above drawback, namely, by heating up the plural foods uniformly when heating up the plural foods simultaneously.